1. Field of the Invention
Blood clotting is a complex chemical process involving a number of constituents. Blood sucking animals have the capability of inhibiting the host's blood from coagulating. There are basically two types of anticoagulant substances: Inhibitors of the clotting catalyst, e.g. inhibitors of thrombin; and fibrinolytic proteases.
The best-understood of these anticoagulants is hirudin, secreted by the leech Hirudo medicinalis. Hirudin is an anticoagulant of the first category, binding irreversibly and with high affinity to human thrombin. Another anticoagulant, of the second category, was obtained from the leech Haementeria lutzi Pinto 1920, which lacks any direct proteolytic activity but activates the host plasminogen.
Depending upon the nature and effectiveness of blood anticoagulants, blood anticoagulants can find a wide variety of applications. Therefore, there has been a continuing interest in obtaining blood anticoagulants which demonstrate different types of anticoagulant activity.
2. Description of the Prior Art
Hirudin has been characterized by Bagdy et al., Methods Enzymol. 45, 669-678, 1976 and Markwardt, Zeitschrift Physiol, Chem. 308: 147-157, 1957. The anticoagulant hementerin from Haementeria lutzi Pinto 1920 is described in an article by Kellen and Rosenfeld, Haemostasis 4: 51-64, 1975.